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NERVOUS SYSTEM › ANALGESICS › OTHER ANALGESICS AND ANTIPYRETICS › Pyrazolones
metamizole sodium
N02BB02
Forms & Strengths
- Oral tablets: 500 mg
- Oral drops: 500 mg/mL
- Solution for injection: 500 mg/mL, 1 g/2 mL
Adult Dosing
- Oral: 500 mg to 1 g up to 4 times daily (max 4 g/day)
- Intramuscular/Intravenous: 500 mg to 1 g single dose, up to 5 g/day in divided doses
Pediatric Dosing
- Oral/IV (children > 3 months or > 5 kg): 8 to 16 mg/kg per dose up to 4 times daily
- Not recommended for infants under 3 months or weighing less than 5 kg
Indications
- Severe acute or chronic pain (e.g., headache, toothache, neoplastic pain)
- Severe pain following trauma or surgery
- High fever refractory to other antipyretics
Mechanism of Action
- Non-opioid analgesic with antipyretic and spasmolytic properties
- Inhibits central and peripheral prostaglandin synthesis
- Scavenges reactive oxygen species and inhibits neutrophil activation
Contraindications
- Known hypersensitivity to metamizole or other pyrazolone derivatives
- Agranulocytosis history or bone marrow function disorders
- Acute intermittent hepatic porphyria and congenital glucose-6-phosphate dehydrogenase deficiency
- Asthma induced by analgesics (ASA triad) or aspirin intolerance
- Third trimester of pregnancy and lactation
Adverse Reactions
- Agranulocytosis (rare, potentially fatal)
- Anaphylaxis, bronchospasm, and severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis)
- Hypotension (especially with rapid IV injection)
- Leukopenia, thrombocytopenia, and aplastic anemia
Drug Interactions
- Methotrexate: increased hematological toxicity
- Cyclosporine: decreased blood concentrations of cyclosporine
- Alcohol: potentiation of adverse central nervous system effects
- Chlorpromazine: risk of severe hypothermia
Curated Content: Needs Vetting Before Put to Clinical Use